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Power Control System for a

Concrete Durability Test Cabinet

Project ID: May08-34

Group Members:

Matt Griffith, EE

Lindsay Spring, EE

Laron Evans, EE

Client:

National Concrete Testing Center

Manager: Bob Steffes

Faculty advisor:

Dr. Gregory Smith

DISCLAIMER: This document was developed as part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. The document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. Document users shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. Such use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced the document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.

December 5, 2007

Table of Contents

Table of Contents 2

Table of Terms 3

Table of Figures 4

Chapter I: Project Plan

Current Situation 5

Problem 5

Customer Need Statement 5

System Block Diagram 6

New System Description 6

Operating Environment 6

Functional Requirements 6

Non-functional Requirements 7

Market Research 7

Deliverables 7

Work Breakdown Structure 8

Project Resources 11

Resource Requirements 12

Project Schedule 13

Signature Page 14

Chapter II: Project Design 15

Design Method 16

Option 1: Design A 17

Option 1: Design B 21

Option 2: Design A 24

Option 2: Design B 26

System Schematic 29

System Wiring Diagram 30

Advantages/Disadvantages 31

Team Recommendation 32

Term

Description

SPST

Single Pole Single Throw. Like a light switch either open or closed.

IC

Integrated circuit. A small chip that has a complex circuit on it.

RS 485

Is a type of connector like an Ethernet plug or serial port.

RS 232

A common port on most computers.

PID

Proportional integrate and derivative control. A general class describing control circuitry.

DIN

A circular cable end with multiple pins. Like a mouse or keyboard connector.

MODBUS

An industry standard serial communications protocol.

ASCII

American Standard Code for Information Interchange. A way to turn letters and symbols in to decimal numbers.

PCB

Printed Circuit Board

Table of terms

Table of Figures

Figure

Description

1

Functional block diagram

2

Option 1 Design A system block diagram

3

Option 1 Design A wiring diagram

4

Option 1 Design A wiring diagram exploded view

5

Option 1 Design B scale drawing of temperature probe

6

Option 1 Design A system block diagram

7

Option 1 Design B system block diagram

8

Existing system schematic

9

Existing system wiring diagram

10

Sample computer user interface.

Current Situation

The National Concrete Testing Center, located in the Town Engineering building, uses a Humboldt H-3185 rapid freeze-thaw cabinet to perform the ATSM C-666 test. It is controlled by a Johnson Controls A72 temperature controller. The temperature recorder is a Supco CR87B. The goal of the current system is to automatically run the C-666 test for about 300 cycles without incident.

Problem

The problem is the current system can’t perform the C-666 test within specifications (documentation included p.asdf). The current control and data recording systems for the test cabinet are not able to perform consistently. Sometimes it isn’t possible to get the concrete samples down to 0°F or up to 40°F. If the test can’t be done consistently then the test cabinet is of little value. Without further testing it isn’t possible to determine if the problem is with the temperature control or with the data recording system or with both.

Customer Need Statement

A completely new system must be implemented to control the heat-cool cycle, and to record the resulting temperatures. The specifications are as follows.

· The heat-cool cycle must be automatically recorded by a computer with the use of National Instrument's LabVIEWTM.

· The data must be displayed on the computer screen as well as recorded to an Excel spreadsheet.

· The user interface must be digitally controlled via an on-site computer.

· The heat-cool cycle must be constant for days at a time without adjustment.

· The system must be scalable to allow the control of both machines in the lab.

System Block Diagram

New System Description

The new system will have a temperature input and a control signal output. The input signal will be the voltage across a thermocouple placed inside one of the concrete blocks in the cabinet. The voltage from the thermocouple will be digitized by the NI USB-6008. Once the temperature data is read into the computer we will be able to use a program written with LabVIEW to decide if the compressor or heating elements should be turned on. For example if the compressor should be on then the USB-6008 will output a 10V signal which will actuate a relay sending 120 VAC to the compressor turning it on.

Operating Environment

The system will operate in an indoor laboratory. We can assume that the room will be kept at normal room temperature. The system will have to operate in dusty and possibly wet conditions. Optimally the system should be mounted under the cabinet to minimize risk.

Functional Requirements

FR 1. The freezing-thawing apparatus shall have automatic controls which are able to continuously reproduce cycles from 0±3°F to 40±3°F.

FR 2. If the control fails it shall fail in a frozen condition.

FR 3. The temperature sensor shall be able to sample various points within cabinet.

FR 4. The heat-cool cycle shall take between 2-5 hours.

FR 5. The time between freezing and thawing phases shall not exceed 10 minutes.

FR 6. The new system shall operate completely separate from the old system.

FR 7. All of the temperature data shall be recorded to an excel spreadsheet.

Non-Functional Requirements

NFR 1. All of the electrical components shall be housed in a waterproof enclosure.

NFR 2. The system shall not cause any fire hazards.

NFR 3. The system shall not cause any electrical shocks.

NFR 4. The user interface shall show a temperature vs. time graph that is open at all times during testing.

Market Research

The company ScienTemp offers a very similar system. Their system contains the following features:

· Touch-screen interface

· On/Off/Auto switch

· On/Off light indicators

· Cycle counter

· Safety interlocks and alarms

· Dedicated computer

There is also the company Humboldt who produces rapid freeze-thaw cabinets that is the same as the current system of this project. Humboldt provides freeze-thaw cabinets with 115V or 230V power rating, 50Hz or 60Hz frequency, and single phase. They also provide heating elements, stainless steel sample positioning tray, recording thermometer chart paper, and other accessories necessary and compatible with the system.

The company Veriteq produces a precision temperature data logger, Spectrum 1000, which has internal sensors, memory and a 10-year lifetime. It has a software package that enables real-time monitoring over an Ethernet network. It is also said to be durable and accurate under cold conditions; its operating range is -40 degrees C to 85 degrees C. It will accept any 100 K ohm thermistor probe compatible with Betatherm 100K6A1.

There are temperature controllers by Delta and Red Lion that are specifically designed to control heating and cooling processes. The power supply needed for the temperature controllers are 100-240VAC. Its input options are an analog, RTD, or thermocouple input. It can be designed for 2-4 outputs and the options are relay, transistor, pulse voltage, and/or linear voltage or current. It includes MODBUS communications, PID control programs, and auto-tuning.

Deliverables

· A computerized system that automatically controls the freeze-thaw cycle

· A sufficient user-interface that allows lab users to input and analyze data

· Two system operation; electromechanical or computerized control

· More accurate temperature sensing; two or three temperature sensors

· Ability to switch system operation

· Automatic system error adjustments

· Manual for future reference

Work Breakdown Structure

Task Name

Complete

Incomplete

% Completion

Project Planning

X

Planning Presentation

X

Plan Review

X

Create Website

X

Retrieve LabVIEW

X

Learn LabVIEW

X

Project Design

X

90%

Design LabVIEW User Interface

X

Design/Build System

X

50%

Design Power Supply

X

Design Input Sensing and Controls

X

Design Output Controls

X

Design New Relay Control integration

X

Design Switch Control integration

X

Design Thermocouple Amplifier

X

Design Communications Scheme

X

Design System Location/Mounting

X

70%

Finalize System Design

X

90%

Design Presentation

X

Design Review

X

90%

Install Relay

X

N/A

Install switch

X

N/A

Integrate New System

X

N/A

Test System Integration

X

N/A

The project will have the following work breakdown:

· Project Planning

· Plan Review

· Create Website

· Project Design

· Design LabVIEW User-Interface

· Design/Build System

· Design Power Supply

· Design Input Sensing and Controls

· Design Output Controls

· Design New Relay Control integration

· Design Switch Control integration

· Design Thermocouple Amplifier

· Design Communications Scheme

· Design System Location/Mounting

· Finalize System

· Design Presentation

· Design Review

· Install Relay

· Install Switch

· Integrate New System

· Test system

Individual and Dual Tasks

Lindsay Spring: Design Input Sensing and Controls


Design Switch Control integration

Install Switch

Design Communications Scheme

System test/diagnosis

Laron Evans:Design Power Supply

Design Output Controls




Matt Griffith:Design LabVIEW user-interface

Design Input Sensing and Controls


Install Relay

Design Thermocouple Amplifier


Project Resources

Resource Requirements

Resources are engineers Lindsay Spring, Laron Evans, and Matt Griffith. The faculty advisor is Dr. Greg Smith and the management consultant is Diana Gualillo. The client resource is Bob Steffes. Each engineer has been assigned tasks that will contribute to completing the project on time. Engineers will roughly work 190 to 200 hours to complete the project. The following calculations are from assigning engineer resources to tasks:

Hours:

Lindsay Spring: 192

Laron Evans: 206

Matt Griffith: 192

Project Labor Cost

Lindsay Spring: $1,920

Laron Evans: $2,060

Matt Griffith: $1,920

Materials Cost

Electromechanical Relay, 30A:$30

Solid-State Relay, 30A$50

Control Switch:$5

Power Supply, 15V, 1A:$15

Thermocouple, K-type, -330 to 2200 F:$39.50

Misc.:$20

Total Costs:$6059.5

Total Cost minus labor:$159.50



Project: May08-34

Faculty advisor, client, and engineers please sign, print and date below indicating that you have read and approve the project plan

SignPrint Date

X_________________________X__________________________ X_______

X_________________________X__________________________ X_______

X_________________________X__________________________ X_______

X_________________________X__________________________ X_______

X_________________________X__________________________ X_______



Final Design

Project ID: May08-34

Group Members:

Matt Griffith, EE

Lindsay Spring, EE

Laron Evans, EE

Client:

National Concrete Testing Center

Manager: Bob Steffes

Faculty advisor:

Dr. Gregory Smith

DISCLAIMER: This document was developed as part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. The document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. Document users shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. Such use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced the document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.

December 5, 2007

Design Method

Functional Decomposition

(Figure 1)

Input Specification

Output Specification

The system has one temperature input ranging from 0o to 40oF.

The design will have one SPST relay output which will control the heating and cooling elements in the existing system.

Design

Option 1: NI 6008

Option 2: Delta temp controller

Design A

Thermocouple

RS 485 to RS 232 to computer

Design B

Analog temperature IC

Analog Voltage to NI 6008 to computer

Option 1: Design A

Design A: Use a thermocouple and thermocouple amplifier to send an analog voltage to the NI 6008. Use LabVIEW to make the control decisions. Use the digital output powered by an amplifier to switch a relay connected to the existing system.

If we choose to implement design A using a thermocouple as the temperature sensor the output voltage will be about , which is much smaller than the voltage sensitivity of the NI 6008 (138 mV). Therefore, a thermocouple conditioner along with an additional amplifier will be required. The digital output of the NI 6008 is 8.5 mA which is not sufficient to power the relay (40 mA), so a current amplifier will be needed. All of the electronic components will be placed on an external PCB powered by a wall mount AC to DC converter. The computer will be connected via USB to the NI 6008. Below is a block diagram for design A.

(Figure 2)

Option 1 Design A: Hardware Specifications

NI 6008 Specifications:

· 8 analog inputs

· voltage range -10V to 10V

· sensitivity 138 mV

· 2 analog outputs:


· output current 5 mA

· 12 digital I/O 0-5V

· output current 8.5 mA

· Compatible with LabVIEW

Thermocouple Specifications:

· Provided by client Bob Steffes:

· Make: OMEGA

· Model: PP-T-24-SLE

· Type: T

· Insulation: Polyvinyl

· Wire Type: Solid Wire

· Wire Gage: 24 AWG

· Max Temperature: 221ºF, 105ºC

Thermocouple Conditioner Specifications:

· Model: AD595

· Supply voltage of 5V to 30V

· Gain of 262

· 10 mV/°C sensitivity

Amplifier Specifications:

· Supply voltage of 2.7V to 5.25V

· Gain of 40

· Opterating temperature -40oC to 100oC

Control Relay Specifications:

· Model: G5C-14-DC5

· Type: SPST

· Contact rating of 15A at 125V

· Coil rating at 5VDC at 200mW

Power Supply Specifications:

· Model: WM063-1950-D5

· 5V, 12V, -12V

· .6A, 0.16A, 0.16A

· 6.3 Watts

Transistor Specifications:

· Model: DTC114GSA

· Collector-Emitter voltage max 50V

· Emitter-Base voltage max 5V

· Collector current 100 mA

· Max temperature 150oC

Manual Switch Specifications:

· Make: GC

· Model: 35-110

· Type SPDT

· Current rating 20A 125V

Wiring Diagram

(Figure 3)

External Hardware

(Figure 4)

Component Specifications:

Make

Model

Cost

Thermocouple Conditioner

Analog Devices

AD595

$6.18

Amplifier

Texas Instruments

LPV321

$1.04

Relay

Omron Electronics

G5C-14-DC5

$3.98

Power Supply

Elpac

WM063-1950-D5

$41.00

transistor

ROHM

DTC114GSA

$0.46

USB repeater

Cables to Go

Super Booster

$84.24

Cat 5 Cable

100’

$18.26

PCB and Case

Team Manufactured

$50

Manual Switch

GC

35-110

$3.32

Total Cost Approximation:

Computer less than 15ft from freeze-thaw machine $105.98


Issues:

This is a custom design that will need to be supported.

Option 1: Design B

Design B: Using an IC temperature probe instead of a thermocouple.

If we choose to implement design B using an IC temperature probe and amplifier, the design would require a large amount of custom design and building. The analog IC temperature sensor and an amplifier would be housed inside of a 6” stainless steel probe. It would require using thermal adhesive to attach the sensor to the tip of the probe, and silicone adhesive to secure the amplifier. The rest of the design would be the same as in A; the only difference would be the type of temperature sensor used. A scale drawing of the probe is on the following page.

(Figure 5)


· 8 analog inputs









Amplifier Specifications:

· Supply voltage of 2.7V to 5.25V

· Gain of 40

· Opterating temperature -40oC to 100oC



· Type: SPST



LM235a Analog Temperature Sensor:

· Temp range -40oC to 100oC

· 1oC accuracy

· Linear output

· 10 mV/ oC

· 5V supply voltage


· Model: DTC114GSA






· Make: GC

· Model: 35-110

· Type SPDT



Make

Model

Cost

Temp sensor

National Semiconductor

LM235a

$0.89

Relay

Omron Electronics

G5C-14-DC5

$3.98

transistor

ROHM

DTC114GSA

$0.46

USB repeater

Cables to Go

Super Booster

$84.24

Amplifier

Texas Instruments

LPV321

$1.04

Steel Probe

Omega

SS-38

$8.50

Pressure fitting

Omega

SSLK-38-38

$18.00

Thermal Adhesive

Arctic Silver

AATA-5G

$5.99

Silicone Adhesive

GE

GE284

$3.44

Cat-5 cable

100’

$18.26

Cap

Anderson Barrows

PB61CP

$1.28

Manual Switch

GC

35-110

$3.32




Issues:

Custom design will be required to build the sensor and its case. We aren’t sure how long it would take to make the probe, and that isn’t our area of expertise.

Option 2: Design A

Design A: Using the DELTA temperature controller for control. Temperature data will be sent to the computer using a RS 485 to RS 232 converter.

If we choose to implement design 2A the controller will use PID control to switch the relay output which will be connected to the existing system. The controller will be able to automatically cycle from 0 to 40 degrees F. Temperature data will be logged using LabVIEW.

(Figure 6)

DELTA Temperature Controller Specifications:

· Dual outputs

· PID, ON/OFF, Manual, and PID programmable control

· PID and Auto-Tuning

· Two built-in control output (for heating/cooling control), and alarm output

· Output options: Relay (250VAC, 5A max), DC Current (4-20mA), or Linear Voltage (0-5V, 0-10V)

· RS-485 (MODBUS ASCII/RTU) communication

· One Thermocouple sensor input (all types)

· DIN rail mounting

· Interface programming

· 100-240V supply, 50-60Hz



· Make: OMEGA


· Type: T




· Wire Accuracy: Special Limits of Error

· Max Temp: 221oF, 105oC

RS232/484 Converter Specifications:

· CommFront Technologies

· Port-powered, no external power required

· Data direction auto-turnaround, no flow control is required

· Dimensions (H x W x D): 0.63 x 1.3 x 3.4 in


· Make: GC

· Model: 35-110

· Type SPDT



Make

Model

Cost

Temperature Controller

DELTA

DTB4848-

$90

Cat-5 cable

100’

$18.26

Thermocouple

Omega

PP-T-24-SLE

Provided

RS232/484 Converter

CommFront Technologies

CVT-485-1

$60.90

Manual Switch

GC

35-110

$3.32

Total Cost Approximation: $172.48

Option 2: Design B

Design B: This would be a worst case scenario for the Delta temp controller. This design would just use the linear voltage output of the temperature controller like the thermocouple conditioner and amplifier. We are considering this possibility because having just a single order PID controller might not be enough to provide adequate control of the system. This design would use the temperature controller to sense the temperature and use the NI 6008 for all of the control decisions. Below is a wiring diagram for design 2B.

(Figure 7)


· 8 analog inputs











· Make: OMEGA


· Type: T




· Max Temperature: 221ºF, 105ºC



· Type: SPST




· Model: DTC114GSA





DELTA Temperature Controller Specifications:

· Dual outputs

· PID, ON/OFF, Manual, and PID programmable control

· PID and Auto-Tuning

· Two built-in control output (for heating/cooling control), and alarm output

· Output options: Relay (250VAC, 5A max), DC Current (4-20mA), or Linear Voltage (0-5V, 0-10V)

· RS-485 (MODBUS ASCII/RTU) communication

· One Thermocouple sensor input (all types)

· DIN rail mounting

· Interface programming

· 100-240V supply, 50-60Hz


· Make: GC

· Model: 35-110

· Type SPDT


Make

Model

Cost

Temperature Controller

DELTA

DTB4848-

$90

Cat-5 cable

100’

$18.26

transistor

ROHM

DTC114GSA

$0.46

USB repeater

Cables to Go

Super Booster

$84.24

Thermocouple

Omega

PP-T-24-SLE

Provided

Manual Switch

GC

35-110

$3.32

Relay

Omron Electronics

G5C-14-DC5

$3.98




Connection to the existing system

(Figure 8)

Wiring diagram

(Figure 9)

Software Specification

The PC operating system will run on Microsoft version XP and the LabVIEW will run on a version of no less than 8.0.

User Interface Specification

The user interface will be controlled through a PC computer using LabVIEW software that will collect the temperature data and record it into an Excel spreadsheet.

The following image shows an example of the LabVIEW user interface.

(Figure 10)

Advantages and Disadvantages

Advantages

Disadvantages

Cost

Option 1 Design A: Thermocouple

Design and fabrication within our scope. Easy to write the software.

We would have to make custom circuits and PCBs. External power supply.

Computer

< 15ft $105.98

Computer

< 150ft $208.48

Option 1 Design B:

Analog Temperature IC

If we make multiple probes they would be easy to replace. No external power supply or PCB. Easy to write the software.

Fabrication would be difficult. Little support for probe.

Computer

< 15ft $46.90

Computer

< 150ft $149.40

Option 2 Design A:

RS 485 to RS 232 to Computer

No custom circuits. Delta would provide customer support. Same cost for the computer close or far.

Only first order PID control.

$172.48

Option 2 Design B:

Analog Voltage to NI 6008 to computer

No custom circuits or PCB. Varity of possible combinations. Easy to write the software.

Computer

< 15ft $97.76

Computer

< 150ft $200.26

Team Recommendation

Based on the above three design choices, the team recommendation is for Option 2 Design A, using the DELTA temperature controller. Based on the advantages, it appears that it will be the most cost effective design with minimal custom build therefore requiring minimal support. Also if the controller is unable to perform it would only take an additional $5.00 to change to Design B using the NI 6008. Using the Delta temperature controller has the highest success rate and the most flexibility.

3

Laron Evans

Project Engineer

Team Lead

Lindsay Spring

Project Engineer

Comm. Coor.

Matt Griffith

Project Engineer

Greg Smith

Project Advisor

Course

Coordinator

Bob Steffes

Client

Project Resources

Diana Gualillo

Management

Consultant

Power Control System for


May08-34

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Company Name�

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Company NameDepartment Name�

Title

Company Name/Title

Laron EvansProject EngineerTeam Lead�

Lindsay SpringProject EngineerComm. Coor.�

Matt GriffithProject Engineer�

Greg SmithProject AdvisorCourse Coordinator�

Diana GualilloManagement Consultant �

Bob SteffesClient�

Project Resources

Power Control System forConcrete Durability Test CabinetMay08-34

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